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A251204
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Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock summing to a nonzero multiple of 2.
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1
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180, 1246, 8870, 65040, 489772, 3775022, 29664576, 236740252, 1912108322, 15584536740, 127880485540, 1054537633526, 8727275684760, 72413361371620, 601955189383922, 5010545177519292, 41746084890460636, 348047155647060662
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 18*a(n-1) - 90*a(n-2) + 7*a(n-3) + 576*a(n-4) + 210*a(n-5) - 180*a(n-6).
Empirical g.f.: 2*x*(90 - 997*x + 1321*x^2 + 8130*x^3 + 2475*x^4 - 2430*x^5) / ((1 - 6*x)*(1 - 5*x - 5*x^2)*(1 - 7*x - 12*x^2 + 6*x^3)). - Colin Barker, Nov 27 2018
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EXAMPLE
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Some solutions for n=4:
..2..2..0....0..2..2....2..2..0....1..1..1....1..0..2....0..2..2....2..0..2
..0..0..0....2..0..2....2..2..0....0..2..2....1..0..2....0..2..2....2..2..0
..0..2..0....1..1..1....2..0..0....2..2..0....1..2..0....2..0..2....0..2..0
..0..2..2....2..2..2....0..2..0....2..2..2....1..2..0....0..2..0....2..0..0
..2..2..0....2..0..2....0..0..0....2..0..2....1..0..2....1..1..1....1..1..1
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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